Not a closed system. Even those little sealed terrariums will die if you leave 'em in the dark for long enough.

First up, your book promo selfie is very impressive! I hope I look as good as you do at your age! I'm not as ripped as you are (proof, since you asked) but I'm fairly happy with myself currently. I eat and drink whatever I want on weekends (last weekend I had rather a lot of red wine on Friday night, an entire pizza to myself on Saturday night, and then another pizza on Monday night, so I'm not exactly some masochistic food nazi), and weekdays I eat whatever I want to, but stay under my energy cap (~6500kj or so). I've just started working out again (20 minutes, 3-4 times a week) after 4 month break thanks to the arrival of our daughter. I think it's fair to say that my approach doesn't take a lot of willpower to maintain a steady weight, and I've maintained this weight for more than three years now so I think it's safe to say it's not temporary.

If your goal is to slowly trim 12kg over the course of several years (if I'm rightly interpreting your blog post), then eating a healthy diet and exercising six hours a week will obviously do the trick. However, my post was in the context of people who need to "lose a lot of weight". To do that you need to run a significant energy deficit - ~2500kJ a day seems to be a good target. I challenge you to suggest a diet that will allow you to run that kind of deficit without feeling hungry (and thus, requiring willpower). And not just a diet where you don't want to eat more broccoli, but one where you won't be tempted by the chips at the lunch bar. I can have those chips if I want 'em, as long as I don't go over my cap.

Obesity rates in many first-world countries are due, I believe, to poor health and nutritional education (just witness the flood of replies I've had in this thread saying either "energy balance doesn't affect weight gain/loss" or "energy balance is out of my control") compounded by food that is super tasty but very energy dense and very nutritionally poor, and by food manufacturers pushing ever-bigger portions in a runaway arms race against each other.

Fair enough, I'm used to kilojoules so I wouldn't be surprised if my calorie numbers are out a bit. I was assuming ~8000kJ a day for an average sedentary adult male. (Incidentally, while Wikipedia more or less agrees with that level, This Australian government website seems to think I should need more like 12k kJ... which seems wrong to say the least.)

I'm a few inches shorter than you and work out 3+ times a week, and I aim for ~6k kJ on weekdays, and splurge to maybe ~8k - ~9k on weekends, which has kept me at my target weight (plus/minus a couple of kilos) for the past few years now.

That kind of metabolic disorder does exist, but the numbers I've seen indicate that maybe 1 in 200 people actually have that kind of biological reason for being fat. (Happy to read links to studies with better/more reliable figures?) So while, yes, there are rare people who have a legitimate medical condition, the vast majority of people can lose virtually all of their excess body fat through controlling their energy balance.

(And while your hunger levels are definitely affected to some degree by hormones, that just means you need more self-control to achieve your desired result. The question wasn't "is it easy and fun to lose weight", it was "does calorie control work" and the answer is a demonstrable "yes".)

Um, what? Gonna need a citation on that first part. And even if it's true that you only absorb 1/4 of the energy in your food but your body can step it up to 100% as it chooses, that just means you need to cut your energy intake by 80%, not 20%.

No argument that eating kilojoules as sugar is as bad as (probably worse than) eating kilojoules as fat.

True. Human bodies are pretty good at absorbing calories in food, and the amount of food you eat still sets the upper limit of the amount of energy you can absorb, but still, fair point.

No, it really doesn't, because it really is that simple and it does help people.

Imagine instead of playing a game of football, you just sat down the captain of the Seahawks at a table with a bunch of snacks in front of him. He starts off 2000 points, and each snack he eats makes the other team score a 100 points. If he eats more than 20 snacks, he loses. If he eats less than 20 snacks, he wins. That is literally the game we are discussing, and you're saying that he can't win that game.

OK, I'll bite. Is there anything in cell biology which violates the laws of thermodynamics?

You're absolutely right that some foods have different effects on perceived 'fullness' and hunger levels for the same amount of energy consumed. And sure, this may make it marginally easier or harder for someone to stay at their target energy intake.

It doesn't change the fact that, whether you use a patch or you go cold turkey, in order to quit cigarettes you have to reduce the number of cigarettes you smoke.

The definition of "portions" is a horrible marketing deception. You get a packet of instant pasta that will just fill a small bowl, and it's labeled as "serves 6". Maybe 6 leprechauns. I think the worst one I saw was a 300mL bottle of fruit juice which was labeled as "1.6 serves". Once you accounted for the actual amount in the bottle it had more kilojoules in it than the same amount of Coke.

It's true that some people burn more energy than others, and that those people can (in fact, must!) eat more to maintain a steady weight. That's what "energy balance" means: energy consumed minus energy used! Maybe you naturally burn 10,000 calories a day. If so, you need to eat less than 10,000 calories to lose weight, and more than 10,000 calories to gain weight. More likely, you burn 2000 calories a day, same as the rest of us, and so you should eat less than 2000 calories a day if you want to lose weight.

No matter how much you talk about the different ways the body metabolizes food, or all the different ways different peoples' bodies work, you can't change the fact that to lose weight you personally must eat fewer calories than you personally burn. If you eat fewer calories than you burn, you will lose weight. It's a fact.

Maybe in the last 50 years, with modern medicine, and with specific types of cancer, yes. But historically, cancer has been an almost universal death sentence. Also, there's no such thing as "obsolete DNA", only more or less effective DNA as demonstrated by the phenotypes it produces. If an organism is still around producing offspring generations later, then it's clearly very well adapted to its environment. If it's no longer well adapted, it will die out, solving the 'problem.'

This, absolutely this. I believe the number one reason many people choose to disbelieve that energy balance is the primary determinant for weight gain/loss is simply that they don't like the answer it gives them: That to lose weight, you have to eat less food and that this means sometimes feeling hungry.

Magic, pills, voodoo, fad diets, resonant crystals, homeopathy... ANYTHING but having to exercise self-restraint.

Yep.

You jest, but this is why we have children instead of just living forever. Think of reproduction as, in a sense, compressing all the information required to make an animal down into a much smaller amount of storage medium than the entire animal takes up. That's a far smaller volume for 'bad data' (mutations, genetic abnormalities etc) to exist in. Then the process of 'unpacking' this data applies a bunch of checksum checks (changes are liable to render the embryo non-viable rather than continuing). In the end you have a genetic copy of the parent(s), but with all of the bad data and random junk squeezed out.

It's not as simple as adding extra telomerase to the end of your DNA strands. The reason we have this genetic equivalent of a MAX_LOOPS constant is that once cells have subdivided that many times, they error rate gets too high. Extending cellular life in this manner without some form of added error correction will just result in cancer.